126 mg of 8-allyl-7-methoxy-2,2-dimethyl-4-oxochroman was dissolved in 12 ml of t-butanol-water (1:1) under nitrogen atmosphere. Thereafter, 0.72 g of AD-mix-β was added to the reaction solution, and the obtained mixture was then stirred at room temperature for 24 hours. Thereafter, 0.77 g of sodium sulfite was added to the reaction solution while cooling on ice, and the obtained mixture was stirred at room temperature for 1 hour. The reaction solution was diluted with ethyl acetate, and then washed with a saturated sodium chloride aqueous solution. The organic layer was dried over magnesium sulfate and then filtered. The organic layer was then concentrated under a reduced pressure, so as to obtain 145 mg of 8-(2,3-dihydroxypropyl)-7-methoxy-2,2-dimethyl-4-oxochroman. This compound was used in the following reaction without further purification.
